A group of defence lawyers is calling on the Government to put up or shut up over claims South Auckland public defenders are "gaming" the legal aid system.

Seventeen Manukau-based lawyers have put their names to a letter calling on Justice Minister Simon Power to forward any evidence of corruption to the police or Serious Fraud Office for prosecution.

The letter - which appears in the Herald today - has been prepared in response to a damning report on the legal aid system by Dame Margaret Bazley.

Dame Margaret alleged the justice system had been undermined by more than 200 corrupt lawyers who were rorting the taxpayer-funded system.

The distinguished public servant also accused lawyers of taking backhanders, charging illegal "top-up" fees and grouping together to defraud the legal aid system, which costs New Zealanders $123.9 million a year.

Although she admitted the allegations could not be substantiated, Dame Margaret said she had been told up to 80 per cent of lawyers at the Manukau District Court were "gaming" the legal aid system.

The 17 lawyers who have written to Mr Power - including Irene West, Catriona MacLennan and Ted Faleauto - say the report risks damaging their reputations, even though it contains "not a shred of specific evidence".

"Her comments appear to be based on nothing more than gossip. However, her statements are deeply damaging to our reputations, to our clients' confidence in us and to confidence in the wider legal system," the letter says.

However, Mr Power said Dame Margaret had made it clear what she was told was anecdotal, because no one - including those she described as "responsible lawyers" - was prepared to complain.

"That's why she said she recommended that the Law Society be put on notice, and that there be a system for accreditation and re-accreditation of lawyers - to make sure they're not in the system.

"When someone with as much credibility and as much experience in providing services to the public as Dame Margaret talks in those terms, the Government cannot ignore what she says. Cleaning up legal aid is in the interests of us all, and the Government will act."

The Manukau lawyers' letter also defends criticism of "so-called car boot lawyers", saying that the stress of their clients' lives often means getting to court on time can be a low-priority.

"Going to a lawyer's office in another location and on another day is an even lower priority," the letter says.

In the fallout from the report, Mr Power said the Justice Ministry would take over the running of the Legal Services Agency. Dame Margaret's report also recommended a three-year timeframe for the Law Society to fix any corruption in the legal aid system or face government regulation.

Mr Power upped the pressure on the profession by reducing Dame Margaret's three years to two.

Law Society president John Marshall, QC, said he was taking the corruption claims seriously, but the great majority of legal aid lawyers were persons of integrity.